Transformer oil (also known as insulating oil) is used in oil-filled transformers. From time to time, in order to permit maintenance of the transformer, the transformer oil is removed from the transformer. Recently, to reduce costs, attempts have been made to re-use transformer oil which has been removed from a transformer.
In order for the transformer oil to function properly, the transformer oil must not be mixed with water. The temperature of the transformer oil also must be maintained within a certain range, e.g., between about 100 C and about 110 C. For the transformer oil to be usable after it has been removed from the transformer, therefore, the transformer oil must be heated while it is out of the transformer, i.e., maintained within the temperature range described above. Also, care must be taken to avoid mixing the transformer oil with water. For instance, because such mixing may take place due to water vapor in the air becoming mixed in the transformer oil, it is difficult to avoid inadvertently mixing water into the transformer oil while the transformer oil is moved into, or out of, the transformer. Accordingly, specialized equipment is needed for temporary storage of the transformer oil.
In addition, the volume of transformer oil involved, e.g., for a single transformer, is relatively large. For instance, a single transformer may have between about 90,000 and about 360,000 liters of transformer oil in it.
In the prior art, the attempts to maintain the removed transformer oil within the required temperature range have typically involved attempting to heat a large tank in which the transformer oil is temporarily deposited, for example, using electric heating elements positioned in tank walls. However, the prior art tanks in which heating has been done in this way have not worked well. It has been found that the prior art heating elements in or on the walls of the prior art tanks have provided only localized heating of the transformer oil. The prior art heating elements are not capable of heating the entire volume of transformer oil in the prior art tank with an acceptable degree of uniformity.
Yet another problem with the prior art units is that they generally are constructed to accommodate relatively small volumes of transformer oil, and accordingly a number of the prior art units may be required for temporary storage of the transformer oil from a single large transformer, e.g., so that maintenance work can be done on such large transformer. A road-ready trailer (i.e., in which the load is partially supported by the wheels of the prior art unit) could not hold the volume of transformer oil typically held in a large transformer.